1. Field of the Invention
The invention relates to an electromagnetically actuated gas valve, in particular for the fuel gas supply in gas engines including a valve seat that has at least one flow-through opening and a sealing plate, movably arranged and guided essentially perpendicularly relative to the valve seat, which has at least one discharge opening, arranged adjacent to a barrier surface that corresponds to the flow-through opening of the valve seat, in order to allow for the overall essentially linear flow-through of the fuel gas through the gas valve; the sealing plate is loaded against the valve seat by means of a return spring and can be lifted relative to the opening via a solenoid; and the flow-through opening of the valve seat has, in comparison with a circular surface of the same cross-section, a large sealing edge length; and the opening stroke of the sealing plate is small.
2. The Prior Art
Magnetically actuated injectors are usually employed for the direct allocation of liquid fuels to the combustion chambers of combustion engines, and they are generally configured in the way of a needle valve. This way, with the restricted mounting space that is available and the injector size that results because of this limitation, only very small switched flow diameters can be achieved which, however, allow for a sufficient metering performance to operate the machine thanks to the high energy density of the liquid fuel. But gaseous fuel, at the same injection pressure, requires a flow cross-section that is larger by a multiple value (for injection pressure p1=200 bar approximately by factor 5; for injection pressure p1=5 bar approximately by factor 20) and that can not be realized with the conventional needle valves. Moreover, needle valves have the disadvantage that they require a minimum amount of greasing for wear-and-tear-free operation, which does not take place during operation with gases, transported or stored in liquid form in the vehicle, due to the extremely low dew point.
In an effort to overcome the last referred to problem, seat valves have become known involving configurations that provide for the closing organ to be arranged orthogonally onto the corresponding valve seat, thereby ensuring that any friction movement between seat and closing organ is reliably avoided (refer to, e.g., U.S. Pat. No. 6,182,943). With the assistance of seat valves it is also possible to solve in a particularly simple way the above mentioned problem of the switching cross-sections that are too small. The embodiment that is discussed in the referred to patent, which envisions that the valve is configured with at least two concentric seat edges that are switchably covered with ring-shaped closing elements, allows for sufficiently large switching cross-sections while the construction space is small. The available valve surface can be utilized in a particularly favorable way if stroke and width of the circumferential slot located between the seat edges are selected at a ratio of width/stroke=approximately 2.
Gas injectors of the kind referred to above must exhibit extremely rapid reaction behavior in order to ensure that the necessary metering accuracy is achieved and a sufficiently large ratio between minimum and maximum fuel quantity that can be metered. Among the construction types that are known in the art for solenoids, it is pot magnets, featuring a magnetic coil containing an iron core of an E-shaped or U-shaped cross section juxtaposed by an essentially plain anchoring plate at a short distance, that exhibit very fast reaction behavior with simultaneously large magnetic force. But the high magnetic forces can only be realized at very small distances or air gaps, which means that the stroke available for switching the magnet is also very minimal. In conjunction with the optimal width/stroke ratio outlined above, it results that a particularly favorable embodied example of the known magnet-actuated ring plate valves features a very narrow slot width or radial division.
A special difficulty of the combustion process involving direct fuel allocation into the combustion chamber results from the circumstance that the injectors are exposed to the combustion pressure and the high combustion temperatures. The fuel supply must be safely sealed against the pressure inside the combustion cylinder even at high pressures. With very high fuel pressures that are in the order of magnitude of combustion peak pressures or above, this can be easily achieved in the context of known configurations of seat valves because of the type of actuation that is used there. In these valves, the fuel pressure and a return spring press the sealing element against the valve seat, and it is opened by means of the action of the solenoid acting against these closing forces. For fuel pressures that are considerably smaller than the anticipated combustion peak pressure, the pressure forces that engage across the pressure working surface of the sealed closing elements acting in the direction of the opening must be equalized with the assistance of a return spring that is designed with sufficient strength. The solenoid, on the other hand, must in turn overcome the sum of the closing forces that are acting for the duration of the time that is envisioned for the injection of the fuel during which generally only minimal cylinder pressure is applied. With lower fuel pressures, this task is difficult to achieve because the magnets that have the sufficient strength both with regard to construction volume as well as dynamic reaction behavior are not suitable.
An apparatus that is able to solve the problems referred to above has been disclosed, e.g., in U.S. Pat. No. 6,230,991. This apparatus contains a pressure equalization system that supplies the combustion pressure to a pressure-compensating piston. This way, it is possible to compensate for the compressive force that acts in the direction of the opening. But this embodiment has several disadvantages: the forces that are introduced from the pressure-compensating piston to the valve plate have the ability to effect an undesired deformation of the valve plate resulting in the partial opening of the valve translating into impermissible leakage. The high level of seal tightness that is required for the object constituting the subject-matter in the present context can, with regard to the characteristically high combustion pressures, only be achieved in terms of practical application with single-ring valves with, due to the construction type, minimal utilization of the available valve surface. Moreover, the problem emerges that combustion exhaust may penetrate into the pressure equalization system contaminating or clogging it. Consequently, it is no longer possible to ensure the proper functioning of the apparatus.
It is the object of the present invention to improve a gas valve of the kind referred to in the introduction in such a way that the problems and disadvantages of the known apparatuses of this kind that have been outlined here are avoided and that, in particular, the required extremely fast reaction behavior at high density and minimal needed assembly space will continue to be ensured.